1. Field of the Invention
The present invention relates to a lighting device including an organic EL element and a method for manufacturing the lighting device.
2. Description of the Related Art
In recent years, a light-emitting element (also referred to as an organic electroluminescent (EL) element) in which a light-emitting layer containing an organic compound is provided between a pair of electrodes has been actively developed. Lighting has attracted attention as one of application fields of the light-emitting element. This is because an organic. EL element can be thin and light and enables surface emission, which provides features that differ from those of other lighting devices.
Since an organic EL element can be formed in the form of a film, an element with a large area can be easily formed. A variety of researches has been conducted on lighting devices including organic EL elements (e.g., see Patent Document 1).
However, there is a problem in that an organic EL element easily deteriorates owing to moisture, oxygen, or the like existing in the outside air or the like. For example, a non-light-emitting region (so called a dark spot) is caused in a light-emitting region by moisture, oxygen, or the like, and the whole of the organic EL element eventually becomes unable to emit light. Thus, various suggestions have been made for sealing against entry of moisture, oxygen, or the like from the outside air into organic EL elements (e.g., see. Patent Document 2 and Patent Document 3).
There is another problem in that under the present circumstances, the cost for manufacturing a lighting device using an organic EL element is very high. The high manufacturing cost results in a high price of the lighting device, which lowers the competitiveness of the lighting device including an organic EL element even though it has the above-described features different from those of other lighting devices. In order to spread the lighting device including an organic EL element, cost reduction in terms of both a material and a process is needed.